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under test and reconnecting it, taking care to make a good connection. The unit should then be retested. If
a failing result is repeated, the connection between the power supply cord ground pin and the chassis of the
equipment being tested should be checked and reworked until a passing result is obtained.
In some cases where the leakage current of the equipment under test is high, but still within the
testing parameters of the HT-2800, and the ground continuity of the chassis at the point of attachment of
the Test Return Lead clip is marginal (within 1% of the three ohm failing point), the ground continuity test
light may trigger after the test has commenced. This is due to the high leakage current appearing as a
voltage across the resistance of the grounding connection, which influences the continuity check. (The
continuity check is monitored continuously during the entire test sequence by the HT-2800 for safety
reasons.) We recommend that this result still be treated as a failure. The high resistance ground path
should be checked and reworked before shipment.
*Special calibrations available by internal adjustment. Must be performed by qualified service personnel. See Sec. 5.
Defeating the Ground Check
The continuity check can only be conducted on equipment using a three wire grounded power
supply cord. Some equipment, such as most portable lamps and all double insulated tools, have only a two
wire power supply cord, so the continuity test cannot be conducted.
Please note that defeating the continuity check should not be done except when necessary to test
two-wire devices. The continuity check feature provides an extra level of operator safety because high
voltage will not be applied if the Test Return Lead is not properly connected to the exposed dead metal of the
equipment being tested. If the Test Return Lead is not properly connected, a dielectric withstand failure
may energize exposed dead metal. Additionally, the HT-2800 may not recognize the failure. The test will
continue for its normal length of time, and the HT-2800 may show a "PASS".
To allow the HT-2800 to test equipment using a two wire power supply cord, the continuity check
can be defeated by turning the rear panel Ground Check switch Off. To remind the operator that the
continuity check is not being conducted, both the Ground OK and Ground Open LED's are lit continuously
during each test. When testing with the Ground Check switch Off, the operator must ensure that the Test
Return Lead is properly connected to exposed dead metal of the equipment being tested for safety and to
ensure that the HT-2800 properly reports all failures.
Leakage Test
The HT-2800 leakage test uses a separate low-frequency transformer circuit to check for excessive
leakage between primary power components and ground. There is not a specific leakage current level
pass/fail requirement at this time for most equipment. However, higher than normal leakage current on a
particular part may indicate an assembly or component problem in the primary circuit.
The leakage current is also monitored by the HT-2800 to ensure that excessive leakage does not
keep the Tester from developing full voltage required for the high voltage test. The HT-2800 will provide full
voltage at any leakage current level up to 5 mA. The leakage current trip level is adjustable on the rear
panel.
The leakage test is conducted by shorting the power and neutral conductors of the power supply
cord and applying high voltage between them and the exposed dead metal of the chassis of the equipment
being tested.
Excessive leakage current is not grounds for failure of the dielectric withstand test. Leakage
current is a normal result of capacitance in the primary circuit between neutral or line conductors and
ground. Because the HT-2800 uses dc voltage, the capacitance will not be apparent, and in non-motorized
equipment, high leakage currents should not normally be anticipated. (In dielectric tests of some larger
electric motors, leakage currents of as high as 95 mA are considered acceptable by safety agencies.)
However, higher than normal leakage currents for a particular example should not be ignored. This indicates
problems of low resistance up to a short circuit between line/neutral and ground, and failures should be
investigated. Failure modes are discussed below.
